The "Create Playlists" Preference is a valuable tool within the TuneUp arsenal. When turned on (the default behavior is off),
When checked, TuneUp will create playlists via iTunes (or Windows Media Player) that keep track of the following:
Songs that you have "Cleaned"
Songs that have been flagged as "Dirty" by using Analyze
Songs that cannot be identified by TuneUp
These playlists are grouped into folders for the different categories, and each playlist is named by a time and date stamp. These playlists can be loaded into iTunes (or Windows Media Player) just like any playlist, and they can also be dragged and dropped onto TuneUp (Windows/iTunes only), which comes in handy when using Analyze and Undo.